1. Field of the Invention
The present invention relates generally to methods and apparatus for providing telecommunications services to end user terminals. More specifically, the present invention relates to a line card for use in a remote terminal at an access network node, the line card including an adaptive subscriber line interface circuit (SLIC).
2. Description of the Prior Art
In the telecommunications industry, large scale copper wire loop plants are commonly used to support analog telephones by providing a plain old telephone service (POTS). The commercial importance of using copper wire loop plants to deliver digital services, such as an integrated services digital network (ISDN), in place thereof is increasing all over the world. A new type of service, known as an “x” type digital subscriber line (xDSL) service, has also been successfully introduced into the local loop. For purposes of describing the present invention, xDSL services refers to all common types of digital subscriber line services including asymmetric digital subscriber line (aDSL) services, high speed digital subscriber line (hDSL) services, and single pair digital subscriber line (sDSL) services. An access interface is designed to connect the central office equipment, such as a switch or a router, to the subscriber over the copper wire loop. This interface is known as the network interface.
In conventional systems, an analog interface, known as a subscriber line interface circuit (SLIC), is used to connect to a standard telephone to provide a POTS service. A digital interface, known as the ISDN “U” interface, is used to connect to a ISDN terminal to provide the ISDN BRI 2B+D services. Another digital interface, known as an xDSL interface, is used to provide internet access to an end user terminal device.
In prior art systems, in order to provide different types of telecommunications services, telecommunications operators must use different network interface ports to interface with different subscribers. Each of a plurality of copper wire loops is designated to provide one type of service. The subscriber must only use the loop that is connected to his house for a single designated service.
A local subscriber line is connected to a subscriber between the network interface of the switch and the subscriber terminal. For example, a subscriber might have the option of signing up the service for either POTS or ISDN. When the subscriber is signed up with POTS, the copper loop is connected to a POTS line card. Subscriber line interfaces for a POTS line card commonly provide BORCHT functions and PCM Codec functions. ISDN coding functions include 2B1Q coding and 2B+D functions. When the subscriber is signed up with ISDN service, the copper loop is connected to a ISDN line card. There is no mix and match for the line cards.